1. Field of the Invention
The present invention relates to a light source device emitting a laser beam for an optical scanning device that scans a scanning surface with the laser beam.
2. Description of the Related Art
In a typical image forming apparatus forming an image with a laser beam, an image is formed, for example, in such a manner that a surface of a photosensitive drum is exposed to the laser beam thereby forming a latent image on the surface of the photosensitive drum. The latent image is developed into a toner image. The toner image on the surface of the photosensitive drum is transferred onto a recording medium such as a sheet, and the transferred toner image is fixed on the recording medium. Such an image forming apparatus has been often used in an on-demand printing system for an easy printing. There have been increasing demands on the image forming apparatus to form an image at high density and to output the formed image at high speed.
In response to the demands, recently, there has been developed an image forming apparatus including a light source such as a vertical cavity surface emitting laser (VCSEL) in which multiple light-emitting units are two-dimensionally arrayed in a monolithic manner. Multiple laser beams emitted from the light source make it possible to simultaneously scan a plurality of scanning lines on a scanning surface. Unlike an image forming apparatus employing an edge-emitting laser light source, the image forming apparatus employing the VCSEL splits a laser beam emitted from the VCSEL so as to take out a portion of the laser beam, and detects an intensity of the portion thereby monitoring an intensity of the laser beam emitted toward the scanning surface (see, for example, Japanese Patent Application Laid-open No. 2003-132580).
In an image forming apparatus using a plurality of laser beams, an optical adjustment of an interval between scanning lines on a scanning surface is made, for example, by rotating a light source around an optical axis of an optical system or the like. However, due to the rotation of the light source, relative positions of the light source and a monitoring unit for monitoring the intensity of the laser beam fluctuate disadvantageously.